This invention relates to microwave power dividers and more particularly to microwave power dividers having a plurality of input ports and a plurality of output ports wherein the output ports are decoupled from one another.
The microwave antenna reflector of a communications satellite is often driven by three antenna feed horns arrayed in azimuth and staggered in their common aperture plane to provide a beam shaped to match a particular region on the earth such as Canada or the continental United States. The desired beam shape results from the physical location of the antenna feed horns with respect to one another and the proper phase relationship between the set of three driving signals. The phase slope relationship between the phase of the signals driving the antenna feed horns can be either a positive or negative going linear phase slope referred to in the art as an azimuthal linear phase progression.
It is further desirable in the communication satellite art to have signals with a positive linear phase progression applied to the antenna feed horns in response to a signal emanating from what is known in the art as an even numbered repeater channel. Similarly, it is desirable to have signals with a negative going linear phase progression applied to the antenna feed horns in response to a signal emanating from an odd numbered repeater channel. Such an operation is accomplished in the prior art by a two input port into a three output port (viz., "2-3") phase converter which provides three properly phase output signals only when two input signals of equal magnitude but 90.degree. out of phase are applied to the inputs of the phase converter. A prior art patent exemplary of such a 2-3 microwave phase in U.S. Pat. No. 3,843,941, issued to Hudspeth, et al., on Oct. 22, 1974.
In Hudspeth, a +90.degree. phase difference between the input signals produces output signals having a positive phase progression and a -90.degree. phase difference between the input signals produces output signals having a negative phase progression. In the art, this 90.degree. phase difference normally necessitates the use of a 3 db hybrid quadrature junction or coupler unit between the single signal driving source and the two inputs to the phase converter to provide the proper quadrature phase relationship between the input signals to the phase converter.
The present invention provides a power divider which delivers three properly phased output signals in response to only one input signal at one input port. Thus, the present invention eliminates the need for a hybrid quadrature unit to generate the two simultaneously applied input signals in phase quadrature to the power divider. It is to be understood that since only one input need be excited to create a properly phased set of output signals that two different input signals can be applied to the power divider with each input signal being applied to one of the power divider inputs resulting in two different but simultaneous output phase progressions appearing at the power divider output ports.
The present invention also eliminates the need for isolators between the output of the 2-3 microwave power divider and each antenna feed horn. This is because the 2-3 microwave power divider of the present invention provides a greater decoupling between output ports than has otherwise been achievable to date.